>>12815569Anything electric is going to be fairly anemic as a tug, the real niche of electric thrusters is actually to just do station keeping, because they offer lots of delta V but it's trapped behind a huge time investment. Electric thrusters also don't scale up very well, limiting their use in any hypothetical cargo hauling application (if your tug has 50,000 m/s of delta V but can only accelerate itself at 0.001 mm/s^2, it doesn't matter that it still has 6000 m/s of delta V with a 100 ton payload because it will take actual decades to push that payload anywhere).
Chemical tugs don't have the Isp to do orbit-to-orbit transport effectively, unless you're in the asteroid belt (everywhere else where chemical tugs would be useful is far enough out that we'd need major breakthroughs in propulsion tech anyway, so we wouldn't use chemical at that point).
Nuclear thermal tugs have potential, because with simple water propellant achieving a single stage delta V of over 10,000 m/s is very achievable, and achieving over 13,000 m/s is possible, but there's red tape to sort through there, and of course we would need to be smart about our design (using hydrogen would once again do nothing but hamper performance, but the allure of between 900 and 1000 Isp would be difficult for most organizations to avoid being trapped by).
Direct nuclear propulsion has the greatest potential but is also the furthest out in terms of becoming a reality. at this point whether fission or fusion doesn't matter, the propulsion capabilities of direct nuclear are unmatched by anything contemporary.
